Solubility of Metal Precursors in Supercritical CO2: Measurements and Correlations

Knowledge of the solubility of metal precursors in supercritical (sc) CO₂ is a key factor for determining the best operation conditions for the synthesis of supported metallic nanoparticles. In this paper, new experimental solubility data of Cu(acac)₂, Pd(acac)₂, and Pt(acac)₂ in scCO₂ for temperatures from 313 to 353 K and pressures from 10 to 40 MPa are presented and compared with the literature data and correlated with semi-empirical density-based models (Chrastil, extended Kumar and Johnston, extended Bartle, and the original and modified Méndez-Santiago-Teja). In addition, literature data for the solubility of Cu(tmhd)₂, Pd(tmhd)₂, and Pt(cod)me₂ in scCO₂ were also correlated with the above-mentioned models. The best result, i.e., the best agreement between the experimental and calculated solubility datasets, was observed for the Chrastil model. Applying the Chrastil and extended Bartle models, the dissolution, sublimation, and solvation enthalpies were estimated. Furthermore, these correlation results were compared with the results from Ushiki et al., who correlated the solubilities of metal acetylacetonates in scCO₂ from the literature using the PC-SAFT equation of state. This comparison showed that the original Méndez-Santiago-Teja model enabled a better description of the experimental data by a factor of three.